Diethanolamine, a chemical widely used in industrial processes (e.g. cutting fluids) and consumer products (e.g. cosmetics), has been reported to alter hepatic phospholipid composition in rats by competing with choline and ethanolamine incorporation. The present study was initiated to determine if an association exists between hepatic phospholipid changes and toxicity after dermal and drinking water exposure to diethanolamine. Livers of F344 rats and B6C3F1 mice exposed to diethanolamine for 14 or 90 days were analyzed for phospholipid composition by high performance liquid chromatography after extraction with chloroform/methanol. In rats, phosphatidylethanolamine and phosphatidylcholine were decreased after treatment with diethanolamine; whereas in mice, multiple unresolved peaks were present in the regions of phosphatidylethanolamine and phosphatidylcholine elution. These new lipid substances may be involved in the hepatotoxicity of diethanolamine in mice.